Читать книгу Food Chemistry - Dennis D. Miller - Страница 29

Leavening is derived from the Latin word levo which means raising or making light. Batters and doughs containing wheat or rye flour may be leavened by incorporating gases into them. Five gases, either alone or in combination, may be used for leavening: carbon dioxide, water vapor, ethanol vapor, air, and ammonia.

The incorporation of leavening gas into baked goods is most frequently accomplished by either yeast fermentation or chemical leavening:

1 Yeast fermentation of sugars:(1)

2 Chemical leavening:Decomposition of salts:(2) Reaction of acids or acidic salts (HA) with sodium bicarbonate:(3)

In yeast leavened products, the CO₂ is produced slowly, inflating air bubbles that have been previously incorporated into the dough during mixing. In contrast, chemical leavening provides some of the initial nucleating gas and provides a much faster means of inflating existing air bubbles during mixing and baking. When heated, the expanded dough “sets” forming the desired texture and lightness. Although seemingly simple in principle, a basic knowledge of chemical leavening is necessary in order to obtain the correct rate and amount of CO₂ release for a specific application.